In a liquid crystal display device, various retarders are used for optical compensation such as prevention of coloring and expansion of view angles. Retarders used in the liquid crystal display device are in a rectangular shape in general and have an orientation axis in a direction inclined with respect to a side thereof. In a liquid crystal display devices, such a retarder is laminated on a polarization plate such that the orientation axis of the retarder and a polarization transmission axis of the polarization plate get into a desired angle.
As a method of manufacturing a retarder having an orientation axis in a direction inclined with respect to its side as above, such a method is widely known that a transparent resin film (raw material film) is stretched longitudinally or laterally to be oriented so as to obtain a long stretched film and then the stretched film is cut in a rectangular shape with a predetermined angle with respect to the side of the stretched film. However, with this method, even if cutting is done so that the maximum area can be obtained, a cutting loss is generated all the time to lower use efficiency of the stretched film, which is a problem. On the other hand, a long stretched film oriented obliquely with a predetermined angle can be cut away in parallel with the side to increase use efficiency of the stretched film.
A method of obtaining a film with a obliquely oriented orientation axis by stretching has been known. For example, in Patent Document 1, a method for producing a obliquely stretched film which is stretched in a direction oblique to a film longitudinal direction is disclosed in which both side ends of a film is grasped between two rows of chucks running on tenter rails arranged so that traveling distances of the chucks in a predetermined traveling section are different and is made to travel.
Patent Document 2 discloses a method of stretching an optical polymer film characterized in that, in a method of stretching an optical polymer film stretched by giving a tension while holding both side ends of a continuously supplied polymer film by holding means and advancing the holding means in a longitudinal direction of the film, stretching is performed while a locus L1 of the holding means from a substantial hold start point to a substantial hold release point at one side end of the polymer film and a locus L2 of the holding means from the substantial hold start point to the substantial hold release point at another side end of the polymer film, and a distance W between the two substantial hold release points satisfy a relation of |L2−L1|>0.4 W, bearing properties of the polymer film are maintained and a state where a volatile component content is 5% or more is present and then, the volatile component content is lowered while the film is made to shrink.
Patent Document 3 discloses a method for producing a long optical film having an optical axis (orientation axis) being in a direction neither in parallel nor perpendicular to a flow direction of the long film obtained by stretching a long film made of a thermoplastic resin, in which the method for producing a long optical film characterized in that, in a region where the film is substantially stretched, stretching is performed so that magnitude of moving speeds at both opposing side ends in the width direction of the films are equal and the traveling distances are different, and at least one of a pair of jigs holding the width-direction both side ends of the film is moved on a rail in a waved shape with respect to the film surface. Moreover, Patent Document 3 describes that the stretching process may be repeated several times or the stretching process may be performed after stretching in a longitudinal direction or a lateral direction in advance.
However, with these obliquely stretching methods, wrinkles or twists can easily occur obliquely. Thus, it is substantially impossible to obtain a wide film having a uniform thickness in the width direction and an orientation axis uniformly oriented in an oblique direction at 10° or more and 85° or less. Thus, it has not been possible to mass-produce a long and wide optical film industrially in which an orientation axis is oriented obliquely (in a direction largely offset from the film width direction or longitudinal direction).    Patent Document 1: Japanese Patent Laid-Open No. 2-113920    Patent Document 2: Japanese Patent Laid-Open No. 2002-86554 (corresponding to U.S. Pat. No. 6,746,633)    Patent Document 3: Japanese Patent Laid-Open No. 2003-232928